The invention relates an operating device for a rotatable closing element of a valve, in particular a rotating actuator for a disc or throttle valve which can be operated by a pressurized medium, as specified in the preamble of claim 1.
A generic operating device is disclosed in FR-A-2 528 128. In the case of this device the cylindrical housing is in the form of an upper and a lower base and a jacket mounted between these bases, the two cylindrical bases being joined to each other by two stationary longitudinal guides. Each of the latter extends through and guides a piston axially, one which is sealed off from the jacket as it slides. Both the piston and the two cylinder bases are penetrated by a central rotating shaft. Repeated penetration of the piston, first by the longitudinal guides and then by the rotating shaft, necessitates sealing of the piston from a pressurized means chamber formed at all these points of penetration between the piston and the cylinder base next to it and the jacket. A piston shank facing the other cylinder base is provided with two helical guide grooves mounted diametrically opposite each other, grooves which are open in the direction of the projecting cylinder base. The piston shank is connected to one of these projecting cylindrical aprons, one which serves as a stop for the end position of the piston when the interior surface of the adjacent cylinder base is reached. Limitation of the end position in the other direction is ensured by a stop ring mounted in the pressurized medium space and not accessible from the outside in assembly of the operating device.
An operating mechanism with comparable and/or equivalent features is disclosed in DE 297 03 710 U1. This rotating actuator, which is operated in particular with compressed air as pressurized means, is applied by preference for valves in which the closing element may in theory rotate endlessly. Such is the case, for example, with so-called ball and disk valves. In these valves additional measures must be taken to ensure that the rotating actuator involved will be stopped in precisely the angular position required so that adequate sealing is ensured in the seating area. In order to provide a specific prescribed angle of rotation special measures are required for angle of rotation limitation, especially in the area of transformation between linear movement of the piston and rotary movement of the rotating shaft. In the case of the conventional rotating actuator the angle of rotation desired is retained in that a stop segment is mounted on the rotating shaft, at least one fixed stop is in the form of a guide rod, and stop segment and guide rod limit the angle of rotation directly at its exact prescribed value independently of piston stroke.
The conventional rotating actuator presents among others the disadvantage that the stop segment may be adapted to changed angle of rotation relationships only by relatively costly replacement of the segment. Changes in angle of rotation limitation due to wear and tolerances may not be made directly without such replacement. Other conventional rotating actuators either exhibit no features at all as regards angle of rotation limitation and angle of rotation setting (DE 298 14 551 U1; EP 0 622 574 B1) or they do exhibit such features (DE 33 03 872 A1) but are relatively complex in structure and not very maintenance-friendly.
The operating device for a pivotable valve body as disclosed in DE 33 03 872 A1 has a pivotably mounted piston in whose external piston jacket two curving guides in the form of diagonal grooves are incorporated diametrically opposite each other. Driving rollers rotatable about axes fixed in a cylinder wall of the operating devices engage these grooves. A driven shaft for operating the pivotable valve body is connected by force fitting inside the piston to the latter both axially and radially. In this design the piston accordingly executes both a stroke movement against the force of a reset spring and in addition the desired rotary movement of the driven shaft, so that a seal sealing the piston from the cylinder wall must execute this total movement resulting from piston stroke and angle of rotation. A form of movement such as this entails increased sealing wear. In addition, the operating device is not particularly assembly and maintenance friendly because of its complex structure, and especially because of the carrier rollers rigidly mounted internally on the cylinder wall.
Also prescribed for the rotating actuators for disk valves is the requirement that a higher torque than that in the angle of rotation area upstream or downstream be available during introduction of the closing element into or removal from the seating seal. According to the rules of conservation of energy, this means that in the course of drive movement a relatively small angle of rotation of the rotating shaft corresponds to a relatively large axial piston stroke. The helical guide groove is for this reason provided with varying pitches. Printed publication EP-B-0 622 574 B1 explicitly illustrates (FIG. 3) and describes a configuration of the guide groove, which, viewed as a whole, is not configured to be symmetrical at all points. As a result, the desired course of torque relative to the central position of the closing element may be changed only in one of the end positions, in the present case during opening and closing of the closing piece. It is also proposed in this connection that different associations be made between linear and rotary movement during opening and closing. This is accomplished in that the curve guide has a curved surface coordinated with the opening and closing movement of the valve (pertinent flank surface of the guide groove) each having a different curve gradient.
In order to make use of the generic operating devices as versatile and flexible as possible without the need for especially costly retrofitting operations, it is desirable for it to be possible to use the rotating actuator in air-opening and thus inevitably spring-closing operation and in air-closing and necessarily spring-opening operation. This requires a precise course of the guide groove or one more or less symmetrical at all points. A guide groove such as this is disclosed in U.S. Pat. No. 2,998,805 (FIG. 8). The guide groove there is exactly point-symmetrical in design, so that the pertinent end position of the closing element (closed position or open position) is approached with the same torque characteristic. The other rotating actuators referred to, because of their given kinematics either do not solve the present problem at all (threaded spindle/threaded nut system in DE 298 14 551 U1) or no specific comments are made regarding this aspect.
The object of this invention is to develop a generic operating device which is of simple design and maintenance-friendly, reliable, and versatile in use and with which a desired angle of rotation may easily be set and retained.
This object is attained by the features disclosed in the descriptive portion of claim 1. Advantageous embodiments of the operating device proposed make up the subjects of the dependent claims.
The two guide grooves, which are bounded on all sides by the piston shank and so are self-contained, as a result of their given point-symmetrical design, permit variable and thus universal use of the operating device. Since the course of torque required in the two end areas of the guide groove may be described, the actuator used may be both air-opening and so necessarily spring-closing and air-closing and so necessarily spring-opening. The two alternative solutions differ only in that the closing element of the valve, rotated 90 degrees relative to the other solution, is connected to the operating device in question as claimed for the invention. In addition, reliable and trouble-free use of the operating device is ensured by the two congruent guide grooves of the piston apron mounted diametrically opposite each other. Limitation of the piston stroke on both sides, on one side by application of the frontal end of the piston shank directly or indirectly to the cover element and on the other by application of a piston head adjoining the piston shank directly or indirectly to a stop element which is mounted in a base of the housing, permits precise limitation and setting of a desired angle of rotation. In all three of the embodiments referred to in the foregoing, the stop element is introduced into the housing base from outside the housing, so that in every case precise limitation and setting of the desired angle of rotation from the exterior by simple means is assured.
A first advantageous embodiment provides a stop element which is mounted directly in the base of the housing and is in the form of a fixed stroke limitation element. This stop, which may be screwed into the housing base until tightly and preferably fixed in position may, in conjunction with the measured tolerance of the components of the operating device involved, be assigned dimensions such that the desired initial position of the rotatable closing element of the valve, and additionally an angle of rotation of 90 degrees, are ensured. Presetting and costly adjustment of the stop element are as a rule not necessary.
The initial position of the rotatable closing element driven by the operating device can be adjusted with precision with a second embodiment of the proposed operating device. Such adjustment can be accomplished in that a stop element is mounted in a first stop fixing device and the latter is fastened directly in the housing base, and in that the associated end position of the piston may be modified with the stop component in one setting area, which is defined by a small stroke segment xc2x1xcex94S which is comparatively small in relation to the full stroke of the piston.
Should limitation of the angle of rotation in the area of the operating angle amounting to a maximum of 90 degrees be desired in addition to simple adjustment of the initial position of the rotatable closing element of the valve, an additional embodiment of the proposed operating device provides that a stop element is mounted so as to be axially movable in a second stop holding device and the latter is fastened directly in the housing, and that with the stop element the associated end position of the piston may be modified within a setting range which is determined by the full stroke of the piston.
In a preferred embodiment the piston consists of plastic and is jacketed without interruption in a metal supporting tube. The plastic material above all simplifies production of the piston, while the supporting tube serves to stabilize the piston and thereby ensures safety and reliability of operating movements.
Another preferred embodiment of the proposed operating device provides that the lateral axis carries on a bearing journal smaller in diameter, along with the associated guide groove, a bearing bush of highly wear-resistant low-friction material on both sides and in any given engagement area, along with the associated guide groove. As a result of the low-friction and wear-resistant rolling movement, the most favorable conceivable kinematic and kinetic preconditions for reliable and safe progress of movement within the framework of transformation between linear and rotary movement are created between the lateral axis and the congruent guide grooves mounted diametrically opposite each other.
In addition, one advantageous embodiment of the proposed operating device provides that there is removably fastened on the end of the rotating shaft extending through the cover element a coupling element having a square opening in its end section and externally in the end section. This coupling element makes it readily possible to adapt the operating device to different types of valves and different nominal widths which, for example, are present in the form of squares of different sizes on the drive side.
As is additionally proposed, reliable and safe disassembly of the operating device is achieved in that the return spring between the piston head and the cover element is pretensioned and in the process positively compartmented with the transverse axis engaged in the guide grooves, by means of the rotating shaft mounted in the cover element. Since the transverse axis remains in the closed guide grooves, the tension of the pretensioned return spring between the piston head and the cover element may be relieved only to the extent permitted by the pertinent axial extent of the guide grooves.
The ease of maintenance of the proposed operating device is ensured in addition by a preferred embodiment in which the cover element is detachably fastened to the housing. This is accomplished in an especially simple manner by a so-called elastic round wire ring (snap spring), which positively immobilizes the cover element within the cylindrical circumferential wall of the housing but in a way permitting easy removal.
In order to permit return of the piston supported by pressurized means or exclusively by pressurized means, provision is additionally made such that the cover element is sealed off externally from the housing jacket by way of a second seal and radially in the interior from the rotating shaft by a third seal, and such that the space formed between the housing jacket, piston head, and cover element has an opening effecting connection to the exterior.
For the purpose of indication of the particular end position of the operating device another proposal provides that on its frontal surface facing the base of the housing the piston is removably connected to a piston rod which extends through the base of the housing and ends in an additional housing connected to the first housing which is mounted on the other side and into which a feedback communication device is introduced. Since the axial position of the piston forms an unequivocal indicator of the resulting angle of rotation, the latter can transmit data regarding the position of the piston and thus regarding the piston rod connected to it into the housing for the feedback communication device. Suitable feedback communication devices are provided there, ones which either provide an external visual display of the rotational angle position of the drive or transmit corresponding control signals to an associated control device.
In order to achieve steady and jolt-free transition between the individual rotation angle sections, another embodiment provides that the transitions between courses of the guide groove characterized by different pitch angles xcex1, xcex2 are designed with a rounding radius R which is at least as large as the external radius of the bearing bushes.